Boiler having tapered duct elements

ABSTRACT

A boiler wherein the hot combustion gases flow upwardly through ducts to transfer their heat to a fluid such as a liquid which engages the duct walls at the sides of the latter opposition from the duct interiors. The boiler is composed of a number of sections which butt against each other. The face of one section which butts against the face of an adjoining section is formed with a series of vertically extending half channels, and the channels of the butting faces of adjoining sections register to form gas ducts up which the hot combustion gases flow. Each of the butting faces of each section is formed with a series of these half channels located one next to the other so that the butting faces of the pair of adjoining sections form a plurality of upwardly directed ducts for the gases. The ducts taper in an upward direction so as to have at their upper ends outlets which are of smaller cross-sectional area than their bottom inlet ends. Also, inclined fins distributed along the interior of the half channels of one section coact with oppositely inclined fins distributed along the interior of the half channels of the butting section to form helicoidal fins in the interior of the gas ducts, and these fins are located closer to each other in the region of the upper outlet end of the gas ducts than in the region of the lower inlets thereof.

United States Patent 1 1 adam Ferroli Tredicesimo Luciano Boniiacio, Italy [21] Appl. No. 792,077

[221 Filed Jan. 17, 1969 {45] Patented June 29, 1971 [73] Assignee FER Fabbrica Europea Riscaldamento S.P.A.

Gambellara, Vicenza, Italy {72] Inventor 32 Priority Jan. 25, 1968, Nov. 13, 196 33 Italy 1 31 1 12003/68 and 23683/68 [54] BOILER HAVING TAPERED DUCT ELEMENTS 2 Claims, 10 Drawing Figs.

[52] US. Cl 122/225 [51] int. Cl F221) 23/00 [50] Field of Search 122/223,

1/1919 Germany 1,241,335 8/1960 France ABSTRACT: A boiler wherein the hot combustion gases flow upwardly through ducts to transfer their heat to a fluid such as a liquid which engages the duct walls: at the sides of the latter opposition from the duct interiors. The boiler is composed of a number of sections which butt against each other. The face of one section which butts against the face of an adjoining section is formed with a series of vertically extending half channels, and the channels of the butting faces of adjoining sections register to form gas ducts up which the hot combustion gases flow. Each of the butting faces of each section is formed with a series of these half channels located one next to the other so that the butting faces of the pair of adjoining sections form a plurality of upwardly directed ducts for the gases. The

ducts taper in an upward direction so as to have at their upper ends outlets which are of smaller cross-sectional area than their bottom inlet ends. Also, inclined fins distributed along the interior of the half channels of one section coact with oppositely inclined fins distributed along the interior of the half channels of the butting section to form helicoidal fins in the interior of the gas ducts, and these fins are located closer to each other in the region of the upper outlet end of the gas ducts than in the region of the lower inlets thereof.

PATENTEU JUN29 197:

SHEET 1 BF 5 UR Wank? V M{ AT ORNEY PATENIEU JUN29 197:

SHEET 3 BF 5 INVIENTQR r/Pz/ccs/mo 400/9/1 0 xf /fwou ATTORNEY 5 SHEET BF 5 PATENTEU JUN29 197i PATENTEDJUNZSIQYI 3589.343

SHEET 5 [IF 5 A ORNEY BOILER HAVING TAPEEED lD UCT ELEMENTS The present invention relates to a conventionally cast or die-cast metal boiler, preferably cast iron boiler, of the type formed of a series of vertically or slopingly extending elements which are interconnected one after the other and which, following such a combination, at least partially define the combustion chamber, the path for the products of combustion and the path for the liquid to be heated.

It is the main object of the present invention to provide a boiler formed of a series of interconnectable elements, in which boiler, owing to the expedients according to the invention, an increase is obtained in the coefficient of heat transmission between the burnt gases and walls defining the gas path, thus improving, any other conditions being unaltered, the quantity of heat being transferred to the water to be heated.

This object, in addition to other objects which will be more apparent from the following detailed disclosure, are attained by a boiler of the above character, which is essentially characterized in that the elements comprising it define a series of bumt gas ducts extending from bottom to top and which are more or less sloping relative to the horizontal.

According to a particular and preferred foml of the invention, it is contemplated that the burnt gas ducts, as defined by the connected elements, have a cross section gradually getting narrower and passing from an elliptic or rhomboidal section to a section which is also substantially elliptic or rhomboidal, but the major axis of which is rotated through 90 with respect to that of the elliptic section of larger dimensions.

According to another form of the invention and in order to increase the surface through which the heat exchange occurs and to increase the length the flue imparting a rotary motion to the burnt gases, it is contemplated that the ducts travelled by said burnt gases have projections emerging from the walls defining the same. Such projections can comprise a series of ribs or fins obliquely arranged to the longitudinal axis of the duct and, in the case, form therebetween and within said duct a single or multithreaded screw ofa constant or variable pitch.

According to a preferred embodiment, the elements which as combined two by two will define the burnt gas passage ducts, have a series of ribs or fins sloping to the longitudinal axis of the duct and the ribs of one element are offset with respect to the ribs of the other element adjoining the former.

According to an important feature of the invention, provi' sion is made for maintaining as far as possible a constant velocity in burnt gas movement by gradually reducing the section of the ducts wherein such gases move.

According to the invention, the connection of two elements always provides ducts, the cross section of which may have any general shape, however preferably comparable with a circular shape, wherein in each duct the fins of a semiduct are differently arranged with respect to the fins of the adjoining semiduct. More particularly, the obliquity or slope of the fins pertaining to a semiduct (obliquity which is estimated relative to the longitudinal axis of the duct) differs from that of the fins of the corresponding semiduct for the adjoining element and, still more particularly, the slope relative to the duct axis is such that, by orthogonally projecting the fins on a plane containing the contact line or surface between two adjoining elements, the projection of at least one pair of fins, one of which pertaining to a semiduct and the other of which pertaining to the adjoining semiduct, will intersect at a point internally of the projection for the duct as provided by the combination of the two semiducts.

The invention will be better understood from the following detailed disclosure given by mere way of nonrestrictive example of two particular preferred embodiments thereof as illustrated in the appended drawings, in which:

FIG. I is a diagrammatic front view showing one of the boiler elements;

FIG. 2 is a fragmentary top view showing three connected elements of the boiler, the view corresponding to arrow II of FIG. 1;

FIG. 3 is a sectional view substantially corresponding to line III-II] of FIG. I;

FIG. 4 is a sectional view according to line IV-IV of FIG. 1;

FIG. 5 is a sectional view according to line VV of FIG. 1;

FIG. 6 is a front view for another embodiment of an element making up the boiler, such an element being an intermediate element, the end elements differing only by 'being provided with semiducts on one face thereof and not on the other face too;

FIG. 7 is a sectional view according to line A-A of FIG. 6;

FIG. 8 is a sectional view according to line BB of FIG. 6;

FIG. 9 is a sectional view according to line C-C of FIG. 6; and

FIG. 10 is a sectional view according to line D-D of FIG. 6.

Referring to FIGS. 1-5, the boiler comprises a series of elements identical to one another, designated as a whole by numeral 2. At the ends of the boiler is defined by two end elements (not shown) which have a smooth surface towards the outer sides.

The several elements, making up the boiler and defining at the bottom the combustion chamber or furnace 3, are joined together by means of tie rods according to a well-known technique.

On the opposite outer faces, each element 2 comprises a series of semichannels 4, which are converted into a plurality of closed channels 5 by mating. of the corresponding semichannels pertaining to the adjoining element 2, as shown in FIG. 2. In other terms, each element 2 has substantially heightwise a series of adjoining depressions which, along with the depressions of the adjoining element, provide a series ofducts 5 lead ing the burnt gases from combustion chamber or furnace 3 to the boiler top, where they are conveyed to the stack (not shown).

As known, upon a fall in temperature the movement of a burnt gas within a constant section duct will be slowed down with a resulting reduction in the coefficient of heat transmission and hence in the quantity of heat being transferred out wardly of the duct. Therefore, the present invention suggests that the passage section for the several ducts 5, resulting from the combination of elements 2 making up the boiler, be of a gradually decreasing size from bottom. to top, as clearly shown in FIGS. 3, 4 and 5, defining three sections at different levels for a pair of adjacent ducts. Particularly, always as seen in such figures, the lowermost section, shown in fig. 3, substantially corresponds to an ellipse, the intermediate section 4 of smaller dimensions corresponds to a circle and finally, the uppermost section, shown in FIG. 5 and of still smaller dimensions, substantially corresponds to .an ellipse wherein the major axis is, however, rotated through with respect to the lowermost section of FIG. 3.

In order to increase the surface through which heat exchange occurs and to impart an ascensional and rotary motion at an almost constant speed to the burnt gases, it is provided according to the invention the provision for ribs (integral with the elements) within said. ducts 5 and which, as shown, are in the form of fins or flanges 6 sloping to the longitudinal axis of the duct. Slope and pitch of the fins varies from bottom to top, such fins being in a larger number from bottom to top of the relative duct in account of the reduction in volume of the burnt gases in accordance with the fall in temperature resulting from cooling due to the heat exchange. The fins 6 for one of the duct portion halves are offset arranged with respect to those of the other portion half of said duct, whereby, as shown in FIG. 1, the position for the fins in the semiduct (not shown), combining with that which is shown instead in this figure, are those as defined by dashed lines 6a. Thus, it can be supposed that within each duct there would exist a series of sections of different pitch helical threads extending through of the relative semiduct and wherein the sections of turns (fins) of a semiduct are offset with respect to those of the corresponding semiduct.

However, other embodiments are contemplated within the scope of the present invention, wherein the several threads, or more particularly the several turn sections, are so combined with one another as to form single or multithreaded, variable or constant pitch helical fins or ribs.

As clearly seen in the drawing, the fins have a limited radial extension, such that centrally of the duct there will remain an unobstructed path, as clearly seen in the representations for all of the figures.

The boiler elements are internally hollow, or define spaces 7, wherein water circulates, this water being supplied through the inlet header 8 and collecting at the top within a header 9. The headers are formed by the assemblages and connection of the several elements making up the boiler, which elements conventionally have, to this end, tubular lugs or extensions of a longitudinal axis perpendicular to the plane of the elements and connected with the spaces 7 of their own element.

According to the teachings of the invention, a boiler is provided of the type as formed by the assemblage and combination of a series of elements defining a series of decreasing or constant section ducts, extending from bottom to top and with a vertical or inclined axis (as shown in the figures) with respect to this direction, in the case fitted with ribs, fins, projections or lugs which, preferably, are within the ducts in a larger number from bottom to top.

FIG. 6 is a front view showing an intermediate element of the boiler according to a different embodiment. The intermediate element is designated as a whole by numeral 100. On one face there are a series of four semiducts 101, the axes of which are slightly convergent, and on the opposite face there are semiducts 102 also of slightly convergent axes.

The end boiler elements (not shown) also have semiducts of the same slope, but provided only on one face of these elements. I I

Preferably, the elements are made of cast iron. These elements are internally hollow at 103, where they are passed through by the water to be heated, this water arriving at a cooled condition at the inside of the element, that is at 103, through a duct which is provided by approaching the elements to one another and which extends at the lower end thereof, where to this end provision is made for cylindrical lugs 104, the central opening 105 of which forms one of the sections for this duct. More particularly, these cylindrical lugs are provided at a lower edge of the element and communicate through openings (not shown) with a pair of channels 106 and 107 and extending within the lower annular portion of the element designated as a whole at 108. Through these two ducts 106 and 107, the water reaches the inner hollow 103 of the elements, contacting the walls of semiducts 101 and 102, then to reach an upper side extension of the element. This extension is passed through by through holes and is designated at 109, and, when the several elements of the boiler are interconnected, forms the outlet duct for hot water. The coaxial openings 110 establish a communication between the interior 103 of each element and the other connected elements.

The lower annular portion 108 of the several connected elements defines a furnace 111, or at least a portion thereof.

From some level of the ascending sides 108A and 1088 of the annular portion 108, there projects on its faces of the intermediate element 100 a rib 112, starting from the inner side of the ascending sides 108A and 1088 and extending to the upper end of the element. On the right-hand side of FIG. 6, the rib extends with an extension 113 and on the left-hand side terminates flush with the faces of extension 109 The mating between the adjoining elements occurs along the surface of these two ribs 112, in the case by the interposition of sealing material. The mating occurs also at the longitudinal ribs 140 separating from one another the semiducts for the same face of the element.

The plane containing the outer surface of these ribs will hereinafter be referred to as the projection plane and will enable to identify the position of the fins which, as better described in the following, are arranged within each semiduct 101, 102.

As previously mentioned, element 100 has on opposite faces a number of undulations providing the semiducts 101,

102, such undulations being laterally defined by ribs 140. Fins or flanges are arranged within each of the semiducts which, as to semiduct 101, are designated by reference numeral 114, while as to semiduct 102 such fins or flanges are designated by reference numeral 115.

These fins 114, are in a larger number from bottom to top in each semiduct and practically are substantially semiannular flanges lying in planes, such as plane X-X, which are inclined with respect to the longitudinal axis Y of each duct. The fins for the same semiduct may be or not parallel to one another. In any case, it is preferred that the fins of each semiduct have the end thereof lying on the same side of the longitudinal axis of the semiduct at a higher level than that of the other end thereof.

As seen in FIG. 6, fins 115 (shown by dashed lines) are inclined with respect to the longitudinal axis of the semiduct substantially in an opposite direction to that of the fins 114 of semiduct 101. More particularly when two elements are approached to each other, a semiduct 102 will combine with a semiduct 101 forming a unitary duct. By orthogonal projection, i.e. at right angles to the plane of FIG. 1, on a plane containing the outer surface of ribs 112, both the contours of the duct and the fins pertaining to the two semiducts providing said duct, it will be seen that the projections of at least one of the fins of semiduct 102 and at least one of the fins of semiduct 101 intersect internally of the projection in the side contours of the duct.

The products of combustion penetrate into the several ducts (as provided by the connection of the several elements making up the boiler) from the lower end 120. The fins will impart to such products an ascending movement suitably guided and will exhaust from the top portion of the ducts into a collecting chamber (not shown) for being conveyed to the stack.

It will thus be seen that the boiler of the invention is made up of a number of sections which have faces butting against each other. Each of the butting faces of adjoining sections is formed with a series of half channels, and the half channels at the butting faces of adjoining sections register so as to form the gas ducts through which the hot combustion gases flow in an upward direction. These ducts of course have the upper re gions which are of smaller cross-sectional area than the lower regions and they have the internal inclined fins which coact at the adjoining sections to form in each duct a helicoidal guide having more fins at the upper outlet regions of the ducts than at the lower inlet regions thereof. The provision of a series of ducts defined by the abutting faces of a pair of sections results in a much more efficient extraction of heat from gases, as compared with an arrangement where a single open gas passage would be formed between a pair of butting boiler sections.

One of the basic elements of the present invention is to be found in the crossed arrangement of the fins pertaining to corresponding semiducts. in a limit case, only one fin could be provided in each semiduct. The projection of the two fins of each duct will be crossed on the reference plane.

What I claim is:

1. In a boiler, a plurality of boiler sections having faces abutting against each other, and the butting face of each section being formed with a series of substantially vertically extending half channels, the half channels of a pair of butting faces of a pair of adjoining sections registering to define between each pair of abutting sections a plurality of gas ducts through which combustion gases flow in an upward direction from lower open ends of the ducts to upper open ends thereof so that heat can be extracted from the hot gases in said ducts, the lower inlet regions of each duct being of an elliptical cross section while the upper outlet region of each duct is also of an elliptical cross section but has a major axis which is at right angles t0 the major axis of the elliptical section at the lower region of each duct.

2. In a boiler, a plurality of boiler sections having faces butting against each other, and the butting face of each section being formed with a series of substantially vertically exfrom lower open ends of the ducts to upper open ends thereof 5 so that heat can be extracted from the hot gases in said ducts, the ducts formed by the butting faces of a pair of adjoining sections having longitudinal axes which are inclined with respect to each other and converge in an upward direction. 

2. In a boiler, a plurality of boiler sections having faces butting against each other, and the butting face of each section being formed with a series of substantially vertically extending half channels, the half channels of a pair of butting faces of a pair of adjoining sections registering to define between each pair of butting sections a plurality of gas ducts through which combustion gases flow in an upward direction from lower open ends of the ducts to upper open ends thereof so that heat can be extracted from the hot gases in said ducts, the ducts formed by the butting faces of a pair of adjoining sections having longitudinal axes which are inclined with respect to each other and converge in an upward direction. 